Re: [PATCH] media: vicodec: fix out-of-bounds write in FWHT encoder

[Hans Verkuil]

Hi Junrui,

On 01/06/2026 16:57, Junrui Luo wrote:
> vidioc_s_fmt_vid_out() sizes the encoder CAPTURE buffer from the
> compressed descriptor pixfmt_fwht, whose sizeimage_mult is 3:
> coded_w * coded_h * 3 + sizeof(struct fwht_cframe_hdr). fwht_encode_frame()
> encodes one plane per component, and an incompressible plane takes the
> FWHT_FRAME_UNENCODED path in encode_plane(), copying the plane verbatim.
> 
> For a 4-component pixel format all four planes are full resolution
> (width_div == height_div == 1), so a frame that forces every plane
> through the unencoded fallback writes
> sizeof(struct fwht_cframe_hdr) + 4 * coded_w * coded_h bytes, overrunning
> the plane by coded_w * coded_h, which can result in corruption
> of adjacent kernel heap memory.
> 
> Bump pixfmt_fwht.sizeimage_mult from 3 to 4, matching the largest
> components_num among the supported raw formats, so the capture buffer is
> always large enough for the unencoded fallback.
> 
> Fixes: 29a7a5e99080 ("media: vicodec: add support for more pixel formats")

Actually, it's commit b40dc2bf3581 ("media: vicodec: add support for 4 new
RGB32 pixelformats") that introduced this.

Please update the Fixes tag.

> Reported-by: Yuhao Jiang <danisjiang@xxxxxxxxx>

Where was that reported? Is there a URL to the that report?

> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Junrui Luo <moonafterrain@xxxxxxxxxxx>
> ---
>  drivers/media/test-drivers/vicodec/vicodec-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/test-drivers/vicodec/vicodec-core.c b/drivers/media/test-drivers/vicodec/vicodec-core.c
> index 318e8330f16a..3ff2d06742c2 100644
> --- a/drivers/media/test-drivers/vicodec/vicodec-core.c
> +++ b/drivers/media/test-drivers/vicodec/vicodec-core.c
> @@ -63,7 +63,7 @@ struct pixfmt_info {
>  };
>  
>  static const struct v4l2_fwht_pixfmt_info pixfmt_fwht = {
> -	V4L2_PIX_FMT_FWHT, 0, 3, 1, 1, 1, 1, 1, 0, 1
> +	V4L2_PIX_FMT_FWHT, 0, 4, 1, 1, 1, 1, 1, 0, 1
>  };
>  
>  static const struct v4l2_fwht_pixfmt_info pixfmt_stateless_fwht = {

It should be changed here as well, otherwise the test-media regression script
in v4l-utils will fail.

Regards,

	Hans

> 
> ---
> base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8
> change-id: 20260601-fixes-7416dda13cfd
> 
> Best regards,